Transactivation of the 'promoterless' luciferase-encoding vectors pXP1 and pXP2 by C/EBP alpha

Transactivation of the firefly luciferase-encoding vectors, pXP1 and pXP2, by the alpha isoform of CCAAT/enhancer-binding protein (C/EBP) is reported. Thus, these vectors are not 'promoterless' in every cellular context, and transactivation by C/EBP or a closely related factor should be considered as a possible explanation for the relatively high background levels of luciferase production that are occasionally observed after transfection of certain cells with these or other similar vectors.